Instrumented Mole System (IMS) (02-06)

Future planetary surface exploration will undertake several physical and chemical measurements. Some require sub-surface penetration to bring the sensors underground: e.g. for thermal flux investigations, or search for water films on soil grains.

An Instrumented Mole System (IMS) – a system able to insert (without retrieval) a mobile penetrometer carrying a payload of sensors for sub-surface measurements until 5 m depth - was developed and tested. This IMS, intended to be mounted on a Planetary Lander, could potentially be used on future planetary missions. The IMS consists of a double-body mole system, composed of a tractor mole (which houses the hammering section) and a trailed mole (which houses the scientific experiment section) connected by a short cable. This allows the accommodation of the moles disposed at 90 degrees each other in a compact lightweight structure, so minimising the storage volume. The lightweight CFRP structure has also a storage compartment for a long flat cable (3-5 meters) which is used to provide the moles with electrical power and data for their operation.

Instrumented Mole System with tractor Mole

Two mechanisms of the pin-puller type are used to keep the moles constrained for launch and landing. No active deployment mechanism was necessary being the deployment achieved by the reaction to the hammering shocks provided by sets of springs included in the guiding tube. The tractor Mole is 25 cm long, 2.6 cm in diameter and has a mass of 0.43 kg. Its motor delivers energy of 0.1 J every 6 s, with an average power of less than 4 W. The IMS FM mass is 1.4 kg.

A breadboard of the IMS has been manufactured including amongst others a structure (made in carbon fibre) and the mechanisms to secure the moles at launch and landing. The breadboard has been extensively tested in its main constituent part individually and in integrated mode. Once integrated deep soil penetration tests, simulated reduced gravity tests, thermal vacuum/climatic chamber tests and vibration test have been performed with good results [Re 2006].